Telegraphone



H. E. ROYS 'I'ELEGRAPHONE 'Feb. 10, 1942.

Filed July 28, 1959 attorney Patented Feb. 10, 1942 2,272,821 rsmcmnom;

Henry E. Boys, Audubon, N. 3., assignor to Radio Corporation of America,a corporation of Delaware Application July 28, 1939, Serial No. 287,066

1 Claim.

This invention relates to telegraphones and more particularly to animprovement therein adapted to more effectively reproduce highfrequencies or to record or reproduce separate frequency bands orchannels.

In telegraphones as heretofore constructed, the frequencies which couldbe recorded or reproduced were limited by the size of the pole pieces ofthe magnets. If very narrow pole pieces were used, fairly highfrequencies could be used, but the efilciency at low frequencies wasvery poor. If pole pieces of suflicient size to give best response onlow frequencies were used, they were incapable of handling highfrequencies.

Further, only a single recording could be mad on a single record,particularly when the wire type of telegraphone was used.

Since fine steel ribbon has been available, it has been used in thetelegraphones for the reason that the orientation of the magnetizationcould be accurately determined, but it has otherwise been used in thesame manner in which wire was used.

I have discovered that, in using steel ribbon, it is possible to handlea much greater frequency range by properly shaping the pole pieces or byusing a plurality of pole pieces. It is also possible to place aplurality of totally independent records on a single ribbon and theserecords may be made by pole pieces particularly adapted to recordselected frequency bands, the whole being combined on reproduction, orsome of the records may be used as control records for regulating theamplifier on reproduction from the other records, so the recordings mayeven be so placed on the tape that one recording will be placed when thetape is moved in one direction and the other record will be played whenthe tape is moved in the other direction.

This arrangement gives the advantage that better frequency response maybe secured and a much smaller quantity of tape than heretofore requiredmay be used for a given amount of playing time.

One of the objects of the invention is to provide a telegraphone havingan improved frequency response.

Another object of the invention is to provide a telegraphone which iscapable of recording and reproducing both high and low frequencies withequal efficiency.

Another object of the invention is to provide a telegraphone which iscapable of recording and reproducing a plurality of-independentfrequency bands on the same record strip.

'of my invention.

In the telegraphone shown in Fig. 1, the steel ribbon i0 is wound from areel 13 on to a reel M by means of a motor H, which drives anappropriate mechanism, such as a pair of rollers, for feeding the ribbonat a constant speed, and also drives the takeup reel IS. The magneticpickups are generally indicated in this figure at I2.

In the form of the invention shown in Fig. 2, a plurality of differentmagnetic pickups is shown in appropriate relation to the steel ribbon.Any

or all of these pickups may be used as desired.

The pair of pickups Z0 and H, which are of opposite polarities, islocated facing each other on opposite faces of the ribbon adjacent oneedge thereof. The corresponding pair of pickups 22 and 23 is located onthe faces of the ribbon adjacent the other edge thereof. It will beapparent that a record produced by the pickups 20 and 2| will not beaffected by the pickups 22 and 23. Conversely, when the record isreproduced, a record produced by the pickups 22 and 23 will .not bereproduced through the pickups 20 and 2|. The pickups 2i! and 2! will,like the pickups 22 and 23, produce magnetization perpendicular to theflat face of the ribbon. A third pair of pickups 24 and 25 is shownhaving their opposite poles facing the edge of the ribbon and slightlyspaced longitudinally of the ribbon. These pickups will producelongitudinal magnetization of the ribbon at the edge thereof.

Since this magnetization is longitudinal and is,

therefore, perpendicular to the plane of magnetization of the pickups 20and 2|, any record produced by the pickups 24 and 25 will not affectthepickups 20 and 2| and passed therebetween.

The pickups 26 and 21 are relatively narrow pickups applied edgewise tothe film like the pickups 24 and 25 but, in this case, they are appliedto opposite edges of the film and produce transverse magnetization ofthe film edgewise.

The pickups 28 and 29 are spaced longitudinally on the film having, ofcourse, their opposite poles adjacent the surface of the film. Thesepickups, due to their longitudinal spacing, will produce longitudinalmagnetization of the film which will not be picked up to any appreciableextent by any of the other types of pickups described.

There will, of course, be a slight amount of pickup, for example, ofimpulses recorded by a pair of pickups such as 24 and 25, and by such apair of pickups as 28 and 29. Likewise, any of the pickups which producea permanent magnetization of the material which will pass through thefield of any other pair of pickups in such position as to affect thefield within those pickups, will produce a certain amount of result, butthe level of this effect is quite low compared to the sound levelproduced on the pickups by the impulses intended for them. This slightmixture of sound corresponds .more or less to the cross-talk whichoccurs on telephone lines and is of the same general order of magnitude.At the relatively low levels and for the purposes for whichtelegraphones are generally used, this slight cross-talk is negligible.However, pickups arranged as just described may be used so as to avoidany appreciable cross-talk by using, for example, one pair of pickups ofappropriate dimensions for recording the low frequencies and a secondpair of pickups in synchronous position thereto for recording the highfrequencies. The high frequency pickups would, of course, be designed soas to more effectively record and reproduce the high frequencies and,due to the synchronous relation of pickups to any pickup of highfrequency by the low frequency pickups, or vice versa, would produce nodamage whatever and would merely serve to reinforce the output from theother pickups.

Furthermore, one or more pairs of pickups may be used for recording orreproducing synchronous sound as just described, while additionalpickups may be used for recording and reproducing subaudible orsuperaudible control frequencies which would be used, for example, tocontrol the amplification in the reproducers of the audio frequencyportion of the apparatus.

The form of the invention shown in Fig. 3

is not as versatile as that shown in Fig. 2. In this form of theinvention, the pole pieces Ill and 3| are tapered laterally of the film.It has been found that, for more effectively recording and reproducinghigh frequency, very narrow pole pieces must be used. on the other hand,for recording and reproducing low frequencies, narrow pole pieces arenot satisfactory for the reason that the total magnetic flux is notsufficient. Therefore, for low frequencies, larger pole pieces are muchmore satisfactory. In this form of the invention, the lateral taper ofthe pole pieces provides a narrow portion of the pole pieces forrecording and reproducing high frequencies whereby the low frequenciesare more effectively recorded and reproduced by the wider edge of thepole pieces. The use of separate pole pieces for recording differentfrequencies is, in this case, avoided by the shaping of the pole piecesand provision of a common winding forthe recording of both the high andlow frequencies,

If desired, the thicker end of the pole piece which is intended torecord or reproduce the low frequencies may be surrounded by anappropriate conducting ring, such as a copper ring, indicated at 32.This ring or short-circuited turn has the effect of preventing thethicker end of the pole piece from responding to the high frequencies.As a consequence, the high frequency impulses are transmittedpractically entirely through the thinner end of the pole piece, therebyincreasing the efficiency of the high frequencies.

I claim as my invention:

A telegraphone including means for moving a magnetizable ribbon betweenpole pieces, said pole pieces including pole pieces adapted to cooperatewith a portion only of the width of said material, other pole piecesadapted to cooperate with a different portion only of said material,other pole pieces adapted to cooperate with an edge only of saidmaterial, other pole pieces adapted to cooperate with the edges of saidmaterial for transverse magnetization, and other pole pieces cooperatingwith the surfaces of said material for longitudinal magnetization.

HEETRY E. ROYS.

